Precision Frequency Marker
Cryptic letters are codes for Japanese/Chinese
characters. English readers may skip them.
$B:G6a(B12.8MHz$B$N(BTCXO$B!J(B $B29EYJd=~7??e>=H/?64o(B $B!K$,%8%c%s%/20$5$s$J$I$G0B$/=P2s$C(B
$B$F$$$^$9!JNc$($P=)7nEE;R$G0l8D(B200$B1_!K!#$=$NL>$NDL$j!"29EYJQ2=$KBP$7$F(B
$B<~GH?t$,$H$F$b0BDj$K$J$k$h$&$K:n$i$l$F$*$j!"<~GH?t$OHyD4$G$-$k$h$&$K(B
$B$J$C$F$$$^$9!#(B
$B2sO)?^$K$"$k$h$&$K!"(BTCXO$B$+$i$N(B12.8MHz$B$N%/%m%C%/$O(B74HC4060$B$H$$$&(B2$B?J%+%&(B
$B%s%?$G(B1/128$BJ,<~$5$l$F(B100kHz$B$N%/%m%C%/$,:n$i$l$^$9!#$5$i$K(B1/2$B$5$l$F(B50kHz$B!"(B
$B$5$i$K(B1/2$B$G(B25kHz$B$,:n$i$l$^$9!#$l(B
74HC4518$B$H$$$&(BBCD$B%+%&%s%?$G(B1/10$BJ,<~$5$l$F(B10kHz$B$H(B5kHz$B$,:n$i$l$^$9!#(B
$B:G=i$K(B100kHz[email protected]_Dj$7$F(BTCXO$B$r(BJJY$BEy$NI8=`EEGH$H%<%m%S!<%[email protected]$7(B
$B$F$*$1$P!"<~GH?t$,D94|[email protected]$J<~GH?t%^!<%+!<$,$G$-$^$9!#Nc$($P!"(B100kHz
$B$K%;%C%H$9$k$H
Precision Frequency Marker
Recently, cheap TCXO modules with a frequency of 12.8MHz are on the
surplus market(at least in Japan). TCXO stands for Temperature
Compensated X'tal Oscillator. It is a fine-tunable oscillator module
packed in a small can with an excellent frequency stability against
ambient temperature change.
As you see in the schematic diagram, the 12.8MHz clock signal from the
TCXO is divided by 128 with a binary counter 74HC4060 to make a 100kHz
clock. Then, further divided by two and another two to make clock
signals of 50kHz and 25kHz. The 100kHz and 50kHz clocks are again
divided by ten with a BCD counter 74HC4518 to make clocks of 10kHz and
5kHz, respectively.
At first, select 100kHz and zero-in with the standard frequency of
e.g. WWV by tuning the trim-pot of TCXO, then you have a
self-maintained precision frequency marker for your homebrew rigs. If
you select 100kHz clock for instance, then you hear the maker beat
signals every 100kHz with your receiver.
MINOWA, Makoto
7N3WVM
Last revised 1998-06-05.